WO 92/07031 teaches the process for preparing a soluble-stable dispersion of a solid biocide comprising a swellable vinyl polymer with a liquid carrier to enable the incorporation of difficultly soluble biocides into polymer resins.
British Patent No. 2,262,468 describes the application of a composition comprising a biocide in a poly(vinyl alcohol) carrier medium to the surface of a mold or former in order to render a plastic acticle biocidally active during the manufacturing process.
Japanese Sho 62-000544 teaches the incorporation of an antibiotic by premixing it with poly(ethylene glycol) or silicone oil and melt blending the pre-mixture into a polyester resin or by preparing a master batch containing the antibiotic in a higher concentration and melting blending the master batch into the polyester.
While the process for putting biocides into plastics by adding the neat active biocidal compound into the polymer substrate during processing or manufacturing is known, this process can lead to discoloration of the final biocidally active substrate. The instant process involves preparing first a biocide-polyester concentrate which is then subsequently added to the polymer substrate. This leads to a final product which is both biocidally active and is resistant to discoloration.